Dewen Tang

Uniaxial tensile tests were conducted to investigate the mechanical anisotropy of rolled 2024 aluminum alloy sheets subjected to different cryogenic treatment durations along the rolling direction (0°), diagonal direction (45°), and transverse direction (90°). The experimental results indicate that the mechanical properties of the rolled 2024 aluminum alloy are strongly dependent on the treatment process and exhibit pronounced anisotropy. With increasing cryogenic treatment time, the yield strength first increases and then tends to stabilize. The optimal combination of mechanical properties is achieved after cryogenic treatment for 16 h, with the yield strength increasing to 385–390 MPa. Cryogenic treatment has no significant effect on the grain morphology of the matrix, but promotes dislocation multiplication and a more uniform distribution of precipitation features. The anisotropy analysis shows that the yield strength in the 45° direction is consistently lower than that in the 0° and 90° directions. The in-plane anisotropy parameter (IPA) decreased from 4.8% in the condition without deep cryogenic treatment to 3.0% after 4 h of cryogenic treatment, followed by an increase to 6.7% after 24 h. This result indicates that short-term cryogenic treatment can effectively reduce the in-plane anisotropy of the 2024 aluminum alloy.

This study investigates the development of a high-density W-Ni-Fe alloy using liquid-phase sintering and examines its microstructure and mechanical properties. Critical parameters, including sintering time and heating rate, were optimized to achieve enhanced density, microhardness, tensile strength, and γ-ray shielding properties. The results show that optimal sintering conditions (45 min at a heating rate of 30 K/min and a sintering temperature of 1753 K) lead to a uniform dispersion of tungsten particles, with a high-volume fraction of tungsten in the matrix and enhanced bonding within the γ(Ni-Fe) matrix. The alloy achieved a density of 16.99 g/cm³ and exhibited superior mechanical performance, with a tensile strength of 846.66 MPa and an elongation of 10.5%, as well as excellent γ-ray attenuation capabilities. These results demonstrate its suitability for nuclear applications.

The cold-rolled 2024 aluminum alloy sheets were subjected to solution treatments at different temperatures followed by artificial aging. The microstructure and mechanical properties were investigated using Vickers microhardness testing, tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that as the solution temperature increases, the coarse particles gradually dissolved into the matrix. At a solution temperature of 500 °C, the grains become nearly equiaxed with an average size of ~16.47 μm, and no significant grain growth is observed compared to the as-rolled condition. The refined microstructure contributes to excellent mechanical properties. In contrast, when the solution temperature increases to 550 °C, the microstructure shows severe grain coarsening (up to ~61.39 μm), which indicates that overburning occurs, resulting in a drastic deterioration in mechanical performance. As the aging time increases, precipitates become more uniformly and densely distributed throughout the matrix, and the hardness initially increases and reaches a peak after approximately 6 h of aging at 180 °C. The optimal mechanical performance, characterized by a favorable combination of strength and ductility, is achieved at an aging time of 6 h. In summary, the optimal heat treatment condition for the cold-rolled 2024 aluminum alloy sheet is solution treatment at 500 °C for 1 h followed by aging at 180 °C for 6 h, resulting in a hardness of 154 HV, a tensile strength of 465 MPa and an elongation of 13%.

Zirconium alloys are essential materials for nuclear fuel cladding. During a loss-of-coolant accident (LOCA), zirconium alloy cladding can oxidize in high-temperature steam (>1000 °C), generating hydrogen and releasing significant heat. Without timely emergency actions, this can result in hydrogen explosions or nuclear leakage. In this study, titanium nitride (TiN), chromium (Cr), and TiN–Cr composite coatings were deposited on the surface of Zr-4 alloy using the magnetron sputtering method. The coatings’ surface and cross-sectional morphologies were examined using scanning electron microscopy (SEM), and their phase structures were analyzed with X-ray diffraction (XRD). The mechanical properties were evaluated using scratch tests, and their resistance to high-temperature steam oxidation was tested in a tube furnace connected to a steam generator. The results showed that the TiN, Cr, and TiN–Cr coatings exhibited strong adhesion to the Zr-4 substrates, with distinct interfaces and pure phase structures. After high-temperature steam oxidation, cracks appeared on the surfaces of the TiN, Cr, and TiN–Cr coatings, likely due to differences in the thermal expansion coefficients of TiO₂, Cr₂O₃, and residual Cr layers. These cracks created pathways for the oxidizing medium, potentially leading to the oxidation of the substrate or inner layers of the composite coatings. For the Cr and TiN–Cr coatings, despite cracking of the Cr layer and melting of the TiN layer at high temperatures, the residual Cr layer effectively restricted oxygen diffusion into the Zr-4 substrate. This study suggests that layers with low melting points, such as TiN, are unsuitable for composite coatings in high-temperature applications. However, adding a Cr layer on top of the TiN layer to form a TiN–Cr composite coating improves adhesion between the coating and the substrate. The TiN–Cr composite coating functions as an effective diffusion barrier at temperatures up to 1200 °C, comparable to a pure Cr coating.

This study investigates the radiation damage and radiation reinforcement of the control and sensing systems of nuclear robots. Radiation experiments were conducted on key electronic devices to study their radiation resistance, and a shielding structure for radiation reinforcement was designed to meet the radiation resistance performance requirements of the system. The results show that at doses exceeding 1300 Gy, Hall sensors, pressure transducers, and temperature transducers exhibit radiation damage. At doses exceeding 170 Gy, transformers and controllers also show radiation damage. Lithium batteries remain largely unaffected, but packs experience voltage decline. When using Pb and W as shielding materials for Super MC simulation, it was found that at a thickness of 15 mm, the shielding efficiency of the controller and transformer under Pb shielding increased by approximately 84.99% and 52.00%, respectively, compared to 92.23% and 74.47% under W, which had the best shielding effect benefits. By adopting radiation-resistant shielding reinforcement, we can effectively improve the radiation resistance of the controller and transformer. This is crucial for ensuring the reliable operation of nuclear robots in high-radiation environments and providing important data and theoretical support for the development of related technologies.

Carbon/polymer-based flexible electrothermal films, as a Joule heating material with excellent electrothermal properties, good formability, and lightweight, are a very needed material in aircraft wing de-icing systems, flexible electric heating elements, and low-voltage wearable devices. In this study, a series of flexible electrically heated films were successfully prepared using polyimide (PI) as the film-forming substrate and graphene (GE) as the conductive filler. The effects of graphene content on the morphology, microstructure, and electrothermal properties, as well as the mechanical flexibility of the electrothermal films, were systematically investigated. The results showed that the GE/PI electrothermal films not only retained the good electrical conductivity of graphene but also had the excellent mechanical properties and high heat resistance of polyimide. The electric heating film with the addition of 8 wt. % GE can quickly reach 390 °C at 24 V with uniform temperature distribution, and the mass loss at 500 °C is only 0.98 wt. %. A wide range of applications exist in fields such as flexible electric heating elements.

To investigate the effect of different oxidation times on the oxidation behavior of Zr–Sn–Nb alloy in a high-temperature steam environment at 1250 °C, steam oxidation tests were conducted on the Zr–Sn–Nb alloy at 1250 °C for durations ranging from 100 to 5000 s. Microstructural and elemental composition analyses of the Zr–Sn–Nb alloy were carried out using scanning electron microscopy, energy-dispersive x-ray spectroscopy, and optical microscopy. The results showed that in the initial stages of oxidation (0–1000 s), the weight gain per unit area followed a parabolic trend. After 2500 s of oxidation, the weight gain rate significantly increased. In the later stages of oxidation (after 4000 s), the weight gain curve transitioned from a parabolic shape to a linear law. With increasing oxidation time, the thickness of the oxide layer gradually increased. In the early stages (0–2500 s), the growth rate of the oxide layer thickness was relatively slow, but the appearance of micro-pores and cracks was observed. However, after 2500 s, the steam oxidation rate of the Zr–Sn–Nb alloy significantly accelerated, leading to fracture and failure of the alloy specimens. The change in oxide layer thickness over time followed a parabolic law before 2500 s and a linear law after 2500 s. The growth curve of the α-Zr(O) layer within 5000 s also followed a parabolic law.

The isothermal steam oxidation behavior of the Zr−Sn−Nb alloy at 1050 °C was studied. In this study, the oxidation weight gain of Zr−Sn−Nb samples with oxidation durations ranging from 100 s to 5000 s was calculated. The oxidation kinetic properties of the Zr−Sn−Nb alloy were obtained. The macroscopic morphology of the alloy was directly observed and compared. The microscopic surface morphology, cross-section morphology, and element content of the Zr−Sn−Nb alloy were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy disperse spectroscopy (EDS). According to the results, the cross-sectional structure of the Zr−Sn−Nb alloy consisted of ZrO₂, α-Zr(O), and prior-β. During the oxidation process, its weight gain versus oxidation time curve followed a parabolic law. The thickness of the oxide layer increases. Micropores and cracks gradually appear on the oxide film. Similarly, the thicknesses of ZrO₂ and α-Zr versus oxidation time were in accordance with the parabolic law.

High precision parts have been widely used in automobile, aerospace, medical and other fields. Conventional machining methods are difficult to meet the requirements of the high-quality requirements of components, including shape precision, dimensional accuracy, surface finish and surface integrity. Using milling instead of grinding can significantly improve machining efficiency of ultra-precision parts for difficult cut materials, especially high hardness SKD11 hardened steel. To improve the surface quality and the processing surface integrity of the parts, high-speed milling (HSM) can be able to meet the high-quality requirements of components. However, the quality of finish HSM is difficult to control through experiments. Therefore, the modified flow stress model of SKD11 hardened steel based on SHPB experimental is adopted to simulate the high-speed finish milling in this paper. The effect of cutting parameters on chip formation, cutting temperature, stress and cutting force of SKD11 are analyzed. Compared with the experimental data of cutting force of different cutting parameters, the simulation results are the same as the measured data. The results show that the model can predict the performance of the SKD11 high-speed finish milling process accurately.